This study continues to examine the mechanisms underlying sudden cardiac death, myocardial infarction and thrombogenesis. Cases of sudden cardiac death are selected retrospectively based on their pathologic findings which include the extent of coronary vessel obstruction and the sites and stages of infarctions and thromboses. Special histopathologic technics are applied to determine evidence of myocardial damage and the status of acute and subacute coronary vessel lesions. The types and times of clinical manifestations during the onset and pre-onset periods are obtained. These data are systematically analyzed to identify associations that may exist among the clinical and pathologic findings. Emphasis is placed on the selection of cases with moderate atherosclerotic heart disease and non-atherosclerotic heart disease but is not limited to them.